Master adjuster for sensing range



NOV. 17, 1970 J SPRUNG MASTER ADJUSTER FOR SENSING RANGE Filed April 21,1969 I N VEN TOR.

my 6. S ay/v4 lax MM fig M 62% US. Cl. 74-526 4 Claims ABSTRACT OF THEDISCLOSURE A device for sensing and signaling pressure variations aboveand below a selected, adjustable range, and including a diaphragmengaging the actuators of two switches, each of which is supported forswinging toward and away from the diaphragm in response to rotation ofan associated adjusting screw. A master adjusting mechanism is providedfor varying the pressure range, and includes a driving gear meshing withtwo driven gears on the adjusting screws to turn the screwssimultaneously, thereby to adjust the actuating points of the switchesupwardly and downwardly in unison and by equal amounts, the gears beingsandwiched between two plates with clearance for limited axial movementof the driven gears with the adjusting screws.

BACKGROUND OF THE INVENTION This invention relates to the sensing andsignaling of variations in a monitored condition, and relates morespecifically to a sensing and signaling device having an output elementmovable in accordance with the variations, and also having a pair ofsignaling elements that are individually adjustable relative to theoutput element so as to vary the values of the condition at which highand low signals are produced.

One such device is a pressure monitor for the blood pressure in one ofthe lines in a hemodialysis system, or artificial kidney. In such asystem, the blood of a patient flows out of his body through one line ortube, through the dialyzer for the passage of substances in the bloodthrough a semipermeable membrane into a dialysate liquid, and then backto the patients body through another tube. The blood-pressure monitoringtypically takes place at a drip bulb attached to one of the tubes, although the sensing and signaling device may be remotely located.

This device signals both high and low pressures so as to indicate adeparture in either direction from a selected range generally centeredon the initial pressure level found to exist at the beginning of thetreatment. Subsequent variations in pressure are indications ofvariations in blood flow, and can indicate excessive blood flow caused,for example, by an accidental opening of the tubing, or a low blood flowresulting, for example, from a clot.

SUMMARY OF THE INVENTION The present invention resides in a masteradjustment mechanism for changing the high and low limits of theselected pressure range simultaneously and in equal amounts, either upor down, so as to center the range quickly and easily on the actualpressure at the beginning of treatment and also at any other timeadjustment becomes necessary or desirable. More specifically, the mastadjustment mechanism includes a single master adjusting element that isgeared to both signal devices to adjust them simultaneously incorresponding directions.

Other objects and advantages of the invention will become apparent fromthe following detailed description, taken in conjunction with theaccompanying drawings.

"United States Patent O 3,540,305 Patented Nov. 17, 1970 BRIEFDESCRIPTION OF THE DRAWINGS FIG. 1 is a side elevational view of asensing and signaling device equipped with a master adjustment mechanismembodying the novel features of the present invention;

FIG. 2 is a fragmentary cross-sectional view taken substantially alongthe line 22 of FIG. 1; and

FIG. 3 is a fragmentary cross-sectional view taken substantially alongthe line 33 of FIG. 2.

DETAILED DESCRIPTION As shown in the drawings for purposes ofillustration, the invention is embodied in a device 10 for sensing theblood pressure in a tube (not shown) carrying blood between a patientand an artificial kidney, and producing a signal if the blood pressuredeparts from a selected range, for example, plus or minus 20% of theinitial pressure. The signal may be audible, visual, or preferably bothaudible and visual, and also indicates whether the pressure has goneabove or below the range.

For these purposes, the device 10 has two signaling elements 11 and 12in the form of switches connected by wiring 13 to an alarm device 14(FIG. 3) for producing the desired signals. The basic pressure-sensingarrangement is conventional, the device 10 having a hollow housing 15with a sealed pressure chamber 17 (FIG. 2) mounted on its underside andconnected to a tube 18 through which pressure is applied to the chamber.

The upper wall of the pressure chamber 17 is a flexible diaphragm 19which rises with increases in the chamber pressure and falls withreductions in pressure, thus constituting a movable output element ofthe sensing means. An actuating ring 20 is mounted on top of thediaphragm to move back and forth vertically within the housing inresponse to pressure changes.

Directly above the actuating ring 20 are the two signaling switches 11and 12, each having an operator 11a, 12a that extends downwardly intoengagement with the actuating ring to be moved by the ring in accordancewith the movements of the diaphragm 19. As shown most clearly in FIGS. 2and 3, each switch is mounted on a generally horizontal plate 21 that ispivoted at one end about a shaft 22 extending across one side of theinterior of the housing 15, the left side as viewed in FIGS. 2 and 3.Mounted in this manner, the plates 21, and thus the switches, arerockable individually toward and away from the diaphragm to adjust theactuating points of the switches.

The device 10 also includes means for adjusting the actuating point ofeach switch 11, 12. For this purpose, two screws 23 and 24 are threadedthrough the left wall 25 (FIGS. 2 and 3) of the housing, parallel toeach other, and engage flanges 27 upstanding from the left ends of theplates 21, above the pivot shaft 22. Thus, each plate and its upstandingflange forms, in effect, a bell crank sup porting the associated switch,and the angular position of the bell crank about the pivot shaft isdetermined by the axial position of one of the screws 23, 24 relative tothe wall 25 of the housing.

By turning one of the screws 23, 24 in a selected direction, theassociated switch 11, 12 may be moved either closer to or farther fromthe diaphragm 19, and this correspondingly adjusts the chamber pressureat which the switch is actuated to produce the selected signal. Herein,the switch 11 is actuated at the higher level to signal a pressureexceeding the selected range, and the switch 12 is actuated at the lowerlevel to signal a reduction in pressure below the range. While thisarrangement is one suitable sensing and signaling arrangement, it willbe evident to those skilled in the art that the invention is not to belimited to this specific form of sensing device.

3 In accordance with the invention, a master adjustment mechanism isprovided, with an adjusting element 28 accessible from outside thehousing 15, to adjust both adjusting elements 23, 24 simultaneously andequally in corresponding directions in order to maintain a uniformspread or range between the actuation points of the two switches 11, 12.Accordingly, the user simply adjusts the single master adjusting elementuntil the desired pressure level is centered between the upper and lowerlimits, and this eliminates not only the difficulty of making twoseparate adjustments, but also the possibility of changing the spread ofthe preselected range during adjustment.

In the present instance, the master adjusting mechanism is 'mountedbetween two parallel plates 29 and 30 supported outside the left wall 25on screws 31 and spacer sleeves 32, the master adjusting element 28being a knob held by set screw 33 on a shaft 34 that is journaled on thetwo plates. The shaft supports a driving gear 35 that is sandwichedbetween the plates and also is disposed between the outer end portionsof the two adjusting screws 23 and 24, as shown in FIG. 3. A pin 37,(FIG. 3) holds the driving gear on the shaft 34.

The driving gear 35 meshes on opposite sides with two driven gears 38and 39 that also are disposed between the plates 29 and 30 and arefastened by pins 40 to the adjusting screws 23 and 24. The totalthickness of the driven gears, including their hubs, is substantiallyless than the spacing between the plates 29 and 30 to accommodate therange of back and forth motion of the gears necessary for the range ofaxial adjustment of the screws and the resulting vertical adjustment ofthe signaling switches. The plates 29 and 30 thus form limiting stopsfor the adjustment mechanism.

It will be seen in FIG. 3 that the driven gears 38 and 39 are free tomove axially relative to the driving gear 35, within the limits of theclearance between the plates 29, 30, without moving out of engagementwith the driving gear. Thus, rotation of the knob 28 in one direction orthe other simultaneously rotates the driven gears 38 and 39 and theassociated adjusting screws 23 and 24 equally in correspondingdirections. This shifts the screws axially by equal amounts to raise orlower the upper and lower actuating points together by equal amounts.

From the foregoing, it will be seen that the present invention providesa novel, and very simple, master adjusting mechanism for selectivelyraising and lowering the acceptable range of pressure variation with asingle and simple motion. It also will be evident that, while a specificembodiment has been illustrated and described, various changes may bemade without departing from the spirit and scope of the invention.

I claim as my invention:

1. In combination with a sensing and signaling device having a housing,a diaphragm in said housing movable back and forth in accordance withchanges in the pressure applied to said diaphragm, first and secondsignal elements actuated by said diaphragm and adjustably positionedrelative thereto so as to change the position of the diaphragm at whicheach signal element is actuated, and a pair of parallel adjusting screwsthreadedly supported in a wall of said housing and each positioning oneof said signal elements according to the axial position of the screwrelative to said wall, the improvement comprising: a pair of drivengears fast on said screws outside said Wall for rotary and axialmovement with said screws; motion-limiting surfaces disposed on oppositesides of said gears with clearance accommodating a range of axial motionof the gears sufficient for a selected amount of adjustment of each ofsaid signal elements; a driving gear rotatably supported between saidsurfaces and mesh ing on opposite sides with said driven gears to turnthe latter equally in response to turning of the driving gear; and anadjusting knob connected to said driving gear and accessible fromoutside said housing to adjust both driven gears, and thus both signaldevices, simultaneously and equally in either direction.

2. The combination defined in claim 1 in which said gears are sandwichedbetween two spaced plates outside said wall, said driving gear beingcarried on a shaft journaled on said plates, and said screws extendingthrough said plates with said driven gears fast on the portions of thescrews between the plates.

3. In combination with a sensing and signaling device having a housing,means in said housing for sensing variations in a monitored conditionand including an out put element movable back and forth in accordancewith such variations, first and second signal elements actuatable bysaid output element and adjustable relative thereto in order to changethe position of the output element and the 'value of said condition atwhich each signal element is actuated, and first and second individualadjusting elements operable separately to adjust the positions of therespective signal elements, the improvement comprising: amaster-adjusting element accessible from outside said housing andmovably mounted thereon, and means connecting said master adjustingelement to said individual adjusting elements and operable to shift thesame simultaneously and equally in corresponding directions relative tosaid output element thereby to maintain a uniform range between thevalues of actuation of said signal elements while changing the level ofthe range.

4. The improvement defined in claim 3 in which said individual adjustingelements comprise screws threadedly supported in parallel relation onsaid housing, and said master adjusting element is a knob disposedoutside said housing, and said connecting means include a shaftextending into said housing from said knob and carrying a driving gearrotatable with said shaft, and a pair of driven gears mounted on saidscrews and each meshing with said driving gear to be turned thereby, andthus to turn said screws for movement thereof simultaneously incorresponding directions.

References Cited UNITED STATES PATENTS 2,648,741 8/1953 Starbird 20'0-83X 3,198,925, 8/ 1965 Starrantino 200-172 3,214,985 11/1965 Danek et a1.74-526 X 3,490,342 1/1970 Reis 200--83 X LEONARD H. GERIN, PrimaryExaminer US. Cl. X.R.

